Cl- channels play a critical role in transepithelial Cl transport, cell volume regulation and cell injury. However, the identity, characterization, localization and pharmacological properties of Cl channels remain limited, particularly in renal proximal tubules (RPT). The long-term goal of this research is to identify and characterize novel renal Cl channels in RPT and determine their roles in RPT physiology and pathology. The neuronal glycine receptor (GlyR) and neuronal GABA-A receptor (GABAR) are heteroligomeric, ligand-gated Cl channels. The initial novel finding was the identification of proteins corresponding to the beta-subunits of the GlyR and GABAR in human, rabbit and rat RPT using immunoblot, immunohistochemical, and molecular studies. Adding to the intrigue was the polarized distribution of the beta subunits; the GlyR beta subunit was localized to the basolateral membrane and the GABAR beta subunit was localized to the brush boarder membrane. GlyR alpha subunits were not detected. Since the only known function of GlyR and GABAR beta subunits is the lining of Cl channels, we propose that the RPT express novel Cl channels composed of selective subunits of the GlyR and GABAR. The first step in addressing this hypothesis will be to: Specific Aim I: Develop and use a GlyR beta subunit selective antibody to identify and localize proteins associated with the GlyR beta subunit in human, rabbit and rat kidney, and thereby begin to determine their specific assemblage into complexes, Specific Aim II. Use a GABAR beta subunit selective antibody to identify and localize additional subunits of the GABAR complex in rat kidney, Specific Aim III. Use GABAR subunit selective antibodies and PCR based strategies to identify and localize GABAR subunits in human kidney. Completion of these specific aims will result in the identification and localization of GlyR and GABAR subunits in the kidney of humans and model animals. Identification of these subunit complexes will lead to their electrophysiological characterization and may ultimately result in the development of new pharmacological agents that modulate Cl transport under physiological and pathological conditions.